1. Field of the Invention
This invention relates to paper feed devices which are part of printers and copiers. More specifically, this invention relates to sheet paper feed devices which move single sheets of paper into copy or print positions.
2. Related Art
The art is replete with various paper feed apparatus included in printers and copiers. Most are of a roller type which feeds paper into position for printing. Such related art systems are prone to multi-feeds or misfeeds of paper sheets. In addition, such systems often use relatively large diameter rollers of 2 inches or more to push the paper through the system. A pad is wrapped partially around the roller and retards all but one sheet. The large drive roller or wheel impacts space constraints in the printer and paper that is pushed rather than pulled through a printer can buckle or move in a direction other than where in intended.
The classic paper separation system is a corner separation system as used in typical copy machines. Such systems are limited essentially to standard paper widths and are unable to feed heavier paper widths. Another related art system uses an inclined separator pad mounted on the frame of a separator disposed in the paper path to retard all but one sheet. Such systems can be optimized only for a certain range of sheet media and are very sensitive to separator pad angle.
In addition, such related art systems also tend to misalign paper sheets as they are fed through the system resulting in wrinkles sheets or misaligned print and are prone to buckling and stalling of the paper as it feeds through the system due to misalignment of the leading edge against rollers or guides through the various stages of feed.
As the related art systems age, that is suffer normal wear, the tolerances change and feed problems increase.
Some belt feed patents have also been issued. Such systems are typified by U.S. Pat. No. 5,114,134 to RASMUSSEN. The RASMUSSEN patent has a paper guide of cork which is substantially the width of the paper on which three, roller driven belts pull paper from the paper tray over the cork for separation. Due to the expanse of area covered by the belts and cork and the pull on the paper by the several belts, friction and pressure within the system are significantly increased with a concurrent increase in wear.